Octavo
Book & Publishing Formats · 6 specs
Direct Answer
An Octavo (abbreviated 8vo or 8°) is the premier classical book format created by folding a printer's sheet three times, producing 8 leaves (16 printed pages). Measuring approximately 6 × 9 inches (152 × 229 mm), it has been the dominant format for hardcover literature, scientific treatises, and library books for over four centuries.
Source: Bibliographical Society / Publishers Association · Last reviewed Aug 28, 2026
Specs
| Folding Structure | 3 consecutive perpendicular folds |
| Leaf and Page Yield | 8 leaves (16 printed pages per sheet — a standard 16-page signature) |
| Typical Dimensions | Approx. 6.0 × 9.0 inches to 6.25 × 9.5 inches (152 × 229 mm to 159 × 241 mm) |
| Standard Bookbinding Signature | 16-page signature (sewn through the fold on binding machines) |
| Historical Standard | Standard format for Charles Dickens, Jane Austen, and Darwin's Origin of Species |
| Modern Publishing Descendant | Standard Trade Hardcover and Trade Paperback (6 × 9 in) |
The 16-Page Signature Backbone
The 3-fold Octavo structure is the foundation of modern high-speed commercial bookbinding. Offset presses print 16 pages onto a master sheet. Automatic folding machines make three right-angle folds to produce an Octavo signature, which are gathered and sewn along the spine to create durable hardcover library books.
Ergonomics and Proportions
At approximately 6 × 9 inches, an Octavo volume provides the optimum ergonomic reading balance: broad enough to display 60 to 70 characters per line without eye strain, yet compact enough to hold comfortably in one hand.